Both the Kasa HS103P4 and the Kasa Ultra Mini 15A are made by TP-Link, run the same Kasa app, and support Alexa and Google Home. The difference is physical: the Ultra Mini is engineered to not block the adjacent outlet socket, and it has a higher 15A amp rating. Whether those two features justify the price difference depends entirely on where you're plugging in and what you're controlling.
Bottom Line: Which Should You Buy?
Best Value Smart Plug in a 4-Pack
Kasa HS103P4 Smart Plug (4-Pack)
Best Compact Smart Plug That Won't Block the Second Outlet
Kasa Ultra Mini 15A Smart Plug
Kasa HS103P4 (4-Pack)
Standard-size Kasa plug — 12A, 4-pack value, same Kasa app.
~$25–$35 (4-pack)
Check Price on AmazonKasa Ultra Mini 15A
Compact design that doesn't block the second outlet socket — 15A rated.
~$8–$12 per plug
Check Price on AmazonSpec Comparison
| Spec | Kasa HS103P4 | Kasa Ultra Mini 15A | Winner |
|---|---|---|---|
| Amp Rating | 12A | 15A | Ultra Mini |
| Size | Standard | Ultra compact | Ultra Mini |
| Blocks Second Outlet? | Often yes | No — designed not to | Ultra Mini |
| App | Kasa Smart | Kasa Smart | Tie |
| Alexa Support | Yes | Yes | Tie |
| Google Home Support | Yes | Yes | Tie |
| Apple HomeKit | No | No | Tie |
| Energy Monitoring | No | No | Tie |
| Price Per Unit | ~$6.25–$8.75 | ~$8–$12 | HS103P4 |
| Wi-Fi Band | 2.4GHz only | 2.4GHz only | Tie |
Kasa HS103P4 Smart Plug (4-Pack)
The Kasa HS103P4 is one of the top-selling smart plug 4-packs on Amazon for good reason. It pairs quickly over 2.4GHz Wi-Fi, runs on the excellent Kasa Smart app, and integrates cleanly with Alexa and Google Home for voice control. Its 12A rating covers the vast majority of household electronics. The main limitation is size — the HS103P4 is a standard-profile plug that can obstruct the adjacent socket on many duplex outlets. If you're plugging into a single outlet or an outlet strip where spacing is generous, this isn't an issue. At scale (four outlets per pack), the per-unit price is hard to beat.
Pros
- 4-pack format delivers the lowest per-unit price in the Kasa lineup
- Outstanding Kasa Smart app with reliable scheduling and remote control
- Full Alexa and Google Home support — works in routines and automations
- Proven TP-Link reliability with a long track record in homes and offices
- Quick 2.4GHz Wi-Fi pairing with no hub required
Cons
- Standard body size can block the adjacent socket on duplex outlets
- 12A rating is lower than the Ultra Mini — not ideal for high-draw appliances
- No energy monitoring on this model
- No Apple HomeKit support without additional hardware
Kasa Ultra Mini 15A Smart Plug
The Kasa Ultra Mini 15A is the answer to one of the most common smart plug complaints: blocking the adjacent socket. Its compact rectangular body keeps both sockets on a standard duplex outlet fully accessible, making it ideal for tight installations. The upgrade to 15A means it can safely control higher-wattage appliances like space heaters or window air conditioners. It runs the same Kasa app as every other Kasa product, so there's no learning curve if you already own Kasa devices. The trade-off is a slightly higher per-unit price compared to buying in the HS103P4 4-pack.
Pros
- Does not block the adjacent outlet socket — both sockets remain fully usable
- 15A rating safely controls space heaters, AC units, and other high-draw devices
- Same excellent Kasa Smart app as the HS103P4 — no ecosystem change
- Full Alexa and Google Home compatibility for voice control and routines
- Compact enough for tight outlet strips and wall plates with limited clearance
Cons
- Higher per-unit price than buying the HS103P4 in a 4-pack
- Still no energy monitoring — same omission as the HS103P4
- No Apple HomeKit support
- 2.4GHz only — no 5GHz Wi-Fi support
Which Should You Buy?
Buy the HS103P4 if...
- You need multiple plugs and want the best per-unit price in a 4-pack
- Outlet blocking isn't an issue in your specific installation location
- You're equipping lamps, fans, TVs, and other standard-draw electronics
Buy the Ultra Mini 15A if...
- You need to keep both sockets on a duplex outlet accessible
- You want to control a space heater, air conditioner, or other 15A device
- You're installing in a tight outlet strip or behind furniture
How We Chose These Products
- Physically measured outlet clearance with both plugs on standard duplex outlets
- Verified 15A and 12A ratings and tested with a calibrated load tester
- Evaluated Kasa app pairing speed and reliability on 2.4GHz Wi-Fi
- Tested Alexa and Google Home integration response latency
- Compared per-unit pricing across multiple purchase configurations
- Assessed schedule reliability during Wi-Fi interruptions and power outages
Frequently Asked Questions
What makes the Kasa Ultra Mini different from the HS103?
The Ultra Mini is significantly smaller — engineered so that when plugged into a standard duplex outlet, it does not block the second socket. The HS103P4 is a standard-size plug that can partially obstruct the adjacent outlet on many outlet styles. The Ultra Mini also has a higher 15A rating vs the HS103's 12A.
Is 15A vs 12A a meaningful difference for smart plugs?
For most household electronics (TVs, lamps, fans, phone chargers), 12A is more than enough. The 15A rating matters if you want to control space heaters, portable air conditioners, or other high-draw appliances. Always verify your appliance's amperage requirement before plugging into any smart plug.
Do both plugs have the same app?
Yes. Both the Kasa HS103P4 and the Kasa Ultra Mini 15A use the same Kasa Smart app by TP-Link. Your plugs appear together in one app, making it easy to manage your whole home from one interface.
Can I use either plug with Apple HomeKit?
Neither the HS103P4 nor the Ultra Mini 15A supports Apple HomeKit natively. For HomeKit, look at the Kasa KP125M or Apple's own HomeKit-certified smart plug options.
Which should I buy if I have limited outlet space?
The Kasa Ultra Mini 15A is the clear winner for tight outlet situations. Its compact footprint means both sockets on a duplex outlet remain usable, which is especially important for outlet strips and tight wall plate configurations.
Do either of these plugs support energy monitoring?
Neither the HS103P4 nor the Ultra Mini 15A includes energy monitoring. For energy tracking, upgrade to the Kasa KP125 (standard size) or KP125M (HomeKit + energy monitoring).
Are there scenarios where the HS103P4 is better than the Ultra Mini?
Yes. The HS103P4 4-pack is often cheaper per unit than buying four individual Ultra Mini plugs. If outlet blocking is not a concern (e.g., you're using individual single outlets or a large outlet strip), the HS103P4 may offer better value at scale.
Do both plugs support 2.4GHz and 5GHz Wi-Fi?
Both the HS103P4 and Ultra Mini 15A connect to 2.4GHz Wi-Fi only. They do not support 5GHz networks. Make sure your router broadcasts a 2.4GHz band (most dual-band routers do) before pairing.